Mechanical seal assembly

Abstract

A mechanical seal assembly adapted to be associated with a rotatable shaft and a housing and having a rotatable seal ring and a stationary seal ring, each having seal faces which engage seal faces on a central seal ring, the latter seal ring being centered only on its outer diameter and being free to rotate relative to the other seal rings thus reducing the speed at the seal faces to the intermediate speed. An aspect of the disclosure is a double spring system wherein seal ring means associated with a shaft and a housing are urged toward one another.

I claims: 
     
       1. In a mechanical seal assembly adapted to be associated with a rotatable shaft and a housing and between a first and second zone each containing a different fluid comprising: a first seal ring having a seal face;   a second seal ring having a seal face;   means connecting said first and second seal rings to said shaft and housing, respectively, permitting limited axial movement of said first and second seal rings; the improvement which comprises:   a central seal ring positioned between said first and second seal rings and having a pair of seal faces, one of which engages said first seal face and the other of which engages said second seal face;   said central seal ring being free of connection with said shaft and said housing and encircling said shaft,   said housing centering said central ring and forming a bearing therefor.   
     
     
       2. A mechanical seal assembly as in claim 1, further comprising resilient means urging said first and second seal rings axially toward said central seal ring. 
     
     
       3. A mechanical seal assembly as in claim 1, further comprising means defining slots in the outer periphery of said central seal ring. 
     
     
       4. A mechanical seal assembly as in claim 3, in which said means defining said slots are acutely angled with respect to said shaft. 
     
     
       5. A mechanical seal assembly as recited in claim 1, wherein said central seal ring has an interior generally cylindrical surface spaced from said shaft and exposed to one of said fluids, said central seal ring interior surface forming a portion of a boundary of one of said zones. 
     
     
       6. A mechanical seal assembly as recited in claim 1, wherein said first seal ring has an interior generally cylindrical surface which is spaced from said shaft and exposed to one of said fluids, said first seal ring interior surface forming a portion of a boundary of one of said zones. 
     
     
       7. A mechanical seal assembly as recited in claim 1, wherein said second seal ring has an interior generally cylindrical surface which is spaced from said shaft and exposed to one of said fluids, said second seal ring interior surface forming a portion of a boundary of one of said zones. 
     
     
       8. A mechanical seal assembly as recited in claim 1, in which each of said seal rings has a generally cylindrical interior surface, each of said interior surfaces being exposed to one of said fluids.